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the general composition and continuation of the world, is indestructible, and as far as we are enabled to comprehend, that the animal and vegetable' parts are continued and sustained by transmutation, and that the general process of nature is to create or compose, by destroying or decomposing
Thus animals forming the superior part of the creation, are endowed with the powers of destroy. ing, masticating, digesting, and decomposing, the substance of both animals and vegetables.
Vegetables, which are more delicately formed, seem peculiarly designed to act in unison with animals, in continuing the animated world, by bringing the divided substances again into action and union,
Animals devour both animals and vegetables to support themselves, and by this they are at the same time made instrumental in preparing the Food of Plants, by facilitating the decomposition of both animals and vegetables.
From the peculiar organisation of vegetables, their food can only be taken up in a state of liquid, and water is the only vehicle by which it can be administered
Whatever therefore constitutes the grand invigorating or accumulating principle in the Food of Plants, must be reducible to a soluble state, or be held in solution. Although water, in its pure state, contains hydrogene and oxygene only, as it is necessarily brought in contact with, or made to
pass through, animal and vegetable substances, which are always scattered over the surface or contained in the soil, before it can come within reach of the roots, it dissolves and carries with it the carbonaceous and earthy matter. Plants possess
power of decomposing water, and in the composition of their own various substances, of retaining and applying the carbon, hydrogene, and earth, and a portion of oxygene,
and at the same time of emitting the superfluous oxygene as excrementitious.
Animals, by respiration, decompose the atmospheric air, retaining part of the oxygene, and emitting the other part united to carbon, (forming carbonic acid gas) and the nitrogene.
Animals and vegetables, when deprived of life and left to spontaneous decay, are decomposed by fermentation, and by this process carbon and earth are deposited ; and oxygene, (which is increased by absorption or attraction) is disposed of, by part forming carbonic oxyde, and part carbonic acid gas; the hydrogene and nitrogene are emitted as simple gas, or united as ammonia.
Carbonic acid gas, or fixed air, is formed by a certain portion of carbon being dissolved and held in solution or combination by oxygene, and is more ponderous than atmospheric air.
These elements, being thus separated, are again combined by the various processes of nature.
By the combustion of electricity, the oxygene gas, emitted by vegetables, and the hydrogene gas,
by putrescent animal and vegetable matter, are united and form water.
By natural affinity, oxygene gas is combined with the nitrogene gas thrown off by the respiration of animals, and atmospheric air formed.
Carbonic acid gas from its density is readily brought in contact with calcareous, carbonaceous, and metallic substances, and also with water, and by these absorbed or decomposed.
COMPOSITION OF SOILS,
AND THE AGENCY OF THE EARTHS IN VEGE
Although the Earth is in fact a variable compound, as it respects vegetation, we need not pursue it farther than the following simple division ; viz. Caly, or the calcareous principle ; Silex, or the silicious; Clay, or the argillaceous; Magnesia, or magnesian; and Carbon, the carbonaceous, or, as it is commonly called, Mould.
The first four substances are what Miller properly calls the containing part or body, bed or couch, and the fifth substance, or mould, (which is the result of decayed animal and vegetable matter) the part contained.
It is clearly proved that neither of the four substances, calx, clay, magnesia, or silex, in a pure state, whether separate or combined, will support a plant; and the vegetative power of every part of the earth is determined by the quantity of mould, or animal and vegetable matter it contains.
Earth is proved to be an essential part of vege
tables ; but the quantity discovered in them is so small, and of such a nature, as to be contained in and conveyed by water.
Too great an accumulation or concentration of vegetable and animal matter, or mould, renders it as a soil unfit for the propagation and sustenance of most vegetables : we therefore find it is in the course of nature divided and diluted, by the intervention and admixture of the other primitive substances, and in this state or combination it forms what is called loam.
Every part of the surface of the globe, that supports vegetables, consists of an admixture or covering of loam, of greater or less depth, and the depth and proportion of the admixture, the degree of exposure to the sun and air, the nature of the substrata, and the quantity of water supplied, determine the produce of the general substance or soil.
It is a very general opinion that carbonic acid gas, or fixed air, constitutes the principal Food of Plants, but this is not demonstrated. Carbonic acid gas, which is composed of carbon held in solution by a large portion of oxygene, is no doubt constituted of the two grand principles of vegetation; but it does not appear to me probable or necessary that it should, in a combined or gaseous state, be applicable as Food; but being decomposed by calcareous earths, the acid neutralized, or the superabundant oxygene withdrawn, by forming some other union, and the carbon united with water, it is then converted into Food.